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1. F. TOOMEY AND 0. s. DEMAREST.

TRANSMISSION CONTROLLING MEANS FOR FOUR-WIRE REPEATERS.

APPLICATION mu) OCT. I6. 1911.

1,318,937. Patented Oct. 14,1919. SSHEETS-SHEET 1. l I 0'65.

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Marilzal IN VEN TORS 7 9 JflTa anjg CJfiemares ATTORNEY 1. F. TOOMEY ANDC. S. DEMAREST.

TRANSMISSION CONTROLLING MEANS FOR FOUR- WIRE REPEATERS. APPLICATIONFILED ocT. I6. 19H- 1 118,937; Patented Oct. 14,1919.

3 SHEETS-SHEET Z- INVENTORS ATTORNEY 760mg 61$. emarest J. F. TOOMEY ANDC. S. DEMAREST.

TRANSMSSION CONTROLLING MEANS FOR FOUR-WIRE REPEATERS.

APPLICATION FILED OCT. 16. I917.

Patented Oct. 14, 1919.

a SHEETS-SHEET 2.

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conrom'rlon or NEW:YO3K.

TRANSMISSION-CONTROLLING ymans non. noun-WIRE nErEArnns.

Beit known that we, Jenn F. :Toonmx [vented certain Improvements 'inTransmission-Controlling Means for Four-Wire flpeaters of, which thefollow-ing s a spec1- f This invention relates to transmission cir.- wcuits, and'niore particularly to transmlssicn fi'cationi.

' circuits of the type known as four-wire -'repeater circuits; One ofthe principal ob] ects over acircuitof this type may be controlled,"although the invention is equally applicable site directionl -In orderto offset theattenproperties ofthe transmission lines, and, if'

a'f'our-wire repeater system as usu'a constructed, two distantstatlons-are co ls; ne ted by two separate transmission-lines,

of the inventionconsists in the provision of linstrumentalities wherebythe transmission "i transmission circuits of any other 'typ one linebeing arranged to transmit signals in one direction,=andthe other linebeing arrangedtotransmit signals in the oppo uation due tothe lengthandelectricaLl desired, to cause a transmission gain: over the four-wirecircuit, one way repeaters may be inserted in each line at suitablepoints. At' theterminal stations the fourwire circuit may beconnectedto-ordinary two-wire lines leading from sa1d term1nat- 'ing'statlons.Inasmuch as the impedance of an operators set may be materially dif-.

, ferentfrom that of the two-wire lines'leading .from terminatingvstations, the transmission efliciency' should be difierent when thefour-wire circuit is. connected: to an operators set, "from thetransmisslon ,efiic1 ency .when'the circuit is connected to .a',two-W1re line. In accordance with this :1n-

vention means'have been provided to 0011- trol the transmission'efiiciency of the four-.- wire circuit in accordance with the circuitto which it'is-connected. Furthermore, the

impedance of the various two-wire lines leading from a terminatingstation of the four-wire system may vary considerably.

It is, therefore, desirable that the transmission over the four-wirecircuit be varied in accordance with the particular type of two-- wireline to which 'it'isconnected. The in- Application filed October s, 1917Serial No. W

SJDEMAREsT, residing at Newl' York city. and. Brooklymrespectively, inthe counties-fof New York and ;Kings,frespectiv ely,"and State of NewYork, have-- in vlever, that any the net-work may be used.

Speciflcation of Letters iatent. 1919.-

" vreiition therefore, contemplates provisionof means whereby thetransmissionover Y the four-wire circuit may be adjusted in accordancewith the two-wire circuit to; which it may be connected. Preferablythe-means whereby; this adjustment is vobtained should be automatic,although thefadjuste.

ment maybe secured either in whole" or in" part by manual manipulations,iiv desired.

When afour-Wire circuit is connected to] a two-wire circuitj it isdesirable-that'the 6 I two-wire circuit bebala'ncedby means of anartificial 1 line Eo'rf net-work, and as the j 'impedances of thelinesvary, net-works".

. should be provided having an impedance r such thatfth'e variouslinesmay be properly 7 0 balanced. Asthe number of'a'rtificial linesrequired mayjin'many instances be less than thenumber of two-wire linesit is sometimes j advantageous to provide equipment wherebythe properartificialli'ne t'o'b'alance' agiven two-wire line may be automaticallyselected.

In accordance with this invention the means I tor automaticallyadJustingthe transmisf s'io'n overthe four-wire circuit is arranged inconpinction. with a means for the auto-8 matic selection of anartificial line, although the transmission adjustment. means may be usedeither with or without the automatic net-work selecting feature. Theparticular,

means herein illustrated for the automatic 8 selection ofthe net-work isthe relay select ing circuit ofthe type illustrated and described in theco-pending application of C.v S. Demarest,'Serial No..174,886,' filedJune 15, 1917. It should be understood, how-v suitable means forselecting" .fjflhe particular means shown for adjust- .ing thetransmission efficiency of the four-f wire circuit consists in aplurality of networks which may be connected in each trans- -missionline. of the four-wire circuit by "meansv of controlling relays.

so that when the four-wire circuit is connected to any line of the samegroup ;thesame adjustment of the transmission is se,-' cured. The linesmay'also be grouped in accordance with the type of net-work necessary tobalance the same. As shown, the grouping of the lines is the same bothfor the selection of artificial lines and for theadjustment of thetransmission efficiency of the four-wire circuit, but it should be understood that the grouping need not be the saine for both purposes.

.The invention will now be more fullyv understood by a reference to thefollowing A description taken in connection with the accompanyingdrawings, Figures 1, 2 and 3 v of which constitute a circuit diagram ofan embodiment of the invention inwhich one 1 end of the four-wirecircuit is equipped with means for the automatic selection of arti- 1licial balancing'lines and for the automatic adjustment of thetransmission of'the fourwirel circuit 'in accordance .with thecharacterv of he two-wire line to which it 'is connected. The other endof the four-wire circuit is illustrate'd as being provided only with ameansfor adjusting the transmission of the four-wire circuit so as tosecure the desired transmission when the circuit-is connected to anoperators set or to a terminating two-wire line. It will be understood,however, that in practice both-ends of the four-wire circuit may"be-provided with the same-type of apparatus, the. terminating apparatusbeing shown-different at the-two ends in the drawin s in order toillustrate two different embodiments of the invention. In order that thecircuit diagram may be. more clearly. understood the sheet upon "whichFig. 1 is placed should be arranged vertically, while the sheets uponwhich Figs. 2 and 3 are placed should. be arranged end to. end .withFig. 2 at the right of Fig. 1.

Referrin' to the drawings, three stations,

A, B and 1% are shown. StationsA and D are connected by transmissionlines E and E for transmission in one direction, and

by lines W and W .for transmission in thev opposite direction, the twosets of'linesthus I forming a four-wire circuit interconnecting the twostations. At station B one-way re-- peaters RE and RWare insertedbetween lines E and E and W and W respec-} tively. It will beunderstood, of course, 1 that the repeaters may be arranged at anydesired point or points-in the lines interconnecting the stations" Aand: D. Itwill also be understood that while the repeaters shown are ofthe so-called mechanical type, repeaters of thevacuum tube typeor of anyother well-known type may be used.-

At station A the four-wire circuit terminates in a jack J 7 whereby aterminating 60 two-wire line may be connected to the fourwire circuit.At station D the four-wire circuit terminates in a jack J 8 for asimilar purpose. Two wire lines L L L L and L 4 are shown terminating injacks J J C terminating in plugs P and P is provided at station A forinterconnecting any one of the two-wire lines at said station with thefour-Wire circuit R. Lines L and L terminate in jacks J and J 6 atstation D, and a cord circuit C, terminating in plugs P and P 1 isprovided for interconnecting any one of said lines with the four wirerepeater B.

.At station A artificial lines N N and N individual to linesL L -and Lare provided to balance said lines, while an arti ficial line RN,adapted to balance either line L or L is provided, said artificial linebeing individual to the fourwire repeater R. A relay selectingarrangement such as that shown and described in the application of C. S.Demarest above. referred to is also provided at'station A for thepurpose of selecting and connecting the proper 'network with thefour-wire circuit to balance the two-wire line with whichit isassociated.

In order to secure the desiredadjustment of the transmission overthefour-wire circuit three net-works are provided at station A'in eachtransmission line of the four-wire circuit. Net works BN EN, and EN areprovided for transmission line E while networks WN N WN are provided forline W One or .m'ore'of these networks may be connected in thetransmission circuit by means of suitable controlling. relays dependingupon the-character of the line to which the four-Wire circuit isconnected. If for any reason the transmission gain due to the four-wirecircuit when connected with any line is too great, means are providedwhereby an operator may connect net-works-EN and in lines E and Wrespectively, thereby reducing the nor mal transmission efiiciency forthat particular connection by a fixed amount,

At station A, in order to balance the fourwire circuit when no terminalapparatus is associated with the two-wire terminals thereof 'and nobalancing artificial line is connected, an impedance arrangementc0mprising series resistances 7 and 7 and a shunt resistance 8 isconnected to the line side of the induction'coil comprising windings 27,28 and 32, while a shunt impedance element 8' is connected across theartificial line side of the induction coil.- These impedance elementsare so proportioned that 1f an operators 'set' is bridged across the zotwo-wire line, or a terminating two-wire lme and an operators set areassociated with theiour-wire circuit, the combination consisting oftheimpedance arrangement 7, 7' and 8 together with the operators set, oroperators set and line as the case may be, will be approximatelybalancedby the impedance element 8 so that the operator may talk or signal overthe four-Wire circuit. When. however. a two-wire line is connected 40,41and 42, whilean impedance element --7-3 is connected across theartificial line side. ,l'sfThe'se arrangements approximately balancethefici'rcuit' when idle, or when an operators s'et"i's"as sociatedtherewith either alone or in with a terminating two-wire line. YVh'en, 1however; a terminating two-wire iodine is connected to the system withno operatorsset associated therewith, the imped ance' arrangements abovedescribed are disconnected and an artificial line or net work N isconnected to the four-wire system to {balance the line As show n but oneartificialiline' is. provided to balance the termi-. natinglines, but itwill be understood that t he"-.c1rcuit' may" be equipped with artificial;-;line-selccting arrangements at station D as "'a'o'i'wellas station Aif desired.

. Withthis general description in the invention-may now be fullyunderstood from aflde eription of the operation. I Assuming that-it is'desired to connect line L at station a 85. and line L, at station Dtothe correspondends, ofthe four-wire repeater R, the

operatornt-jstation A will insert the pi P and 1? ofthe cord-circuit'Cin jack of -li 11'ej.' L and jack J of the-fourwi re circuit 40,respectively. Similarly at station D the op- ."erator will insert plugsPfandP, of cord circuit C in jacks J g and J vrespectively. Upon in-seting the plug P in jack J a circu his closed from ground through theifi-fwindin gof rel'a' ---1, sleeve contacts of jack J and plug and thewinding of relay 2 'tobattery, thereby energizing the relay 2,whiclbeperate's to close the upper strand of the'cord circuit at itsupper contact. Relay $11.1 is marginal'how'ever, and does not receivesuflicientcurrent to energize its winding in series with the highresistance of relay 2. Upon insertingplug P'- in jack J a circuit closedfrom ground through the winding ofrrelay 3, sleeve contacts of jack Jand plug P, and through the Windingof relay "5 to battery, energizingrelay 5. Relay 3, like'relay 1 is marginal, and is not energizedover'thiscircuit. c Q0 Normally the terminating conductors of thefour-wire circuit leading to the tip and ring-terminals'of jack J areconnected-to thefimpedance arrangement consisting of resistances? 8 and7,and resistance 8' is flis'hunted across the artificial line side ofthe winding and back contact'of relay 14, back of whether a terminatingtwo-wire line such as L be connected. ,In order to complete theconnection the operator restores her 11stening key and throwscontrolling key K of the cord circuit C to the left, thereby connectingbattery through a low resistance to the sleeve conductorof plug P overcontact 9 of said key and the upper backcontact of relay 10, whereby thecurrent flow through the windin of relay 1 isinc'reased by an amount sucient to energize said relay. Battery is also applied through a lowresistance to the sleeve contact of plug P over contact 11 of key K andthe lower back 'contact of relay 10, thereby increasing the cur rentflow through the winding of relay 3 by. an amount sufficient to energizesaid relay. A circuit is closed from battery over the front contact ofrelay 3 and through the winding of relay 13. Relay 13 is therebyenergized and opens the shunt through resistances 8 and 8 and shunts theseries re- 1 sistan'ces 7 and17 in the terminating conduct-ors of thefour-wire circuit, thereby changing the transmission efficiency to avalue suitable for a connection over a two'- wire line.

Upon the energizationof relay 1 a momentary circuit is closed fromground over the front contact of said relay through the contact ofrelay-15 to point 16, and thence through the lower winding of relays 17and 18 inseri'es, through resistance 19, back contact and winding ofrelay 20 and front contact of relay 3 to battery. Relays 14, 17, 18

Land 20 are energized over this circuit. Re-

lay 14 at its upper contacts operates to connect artificlalline N, tothe repeater circuit to balance line L, and at its lower contactdisconnects its winding from the selecting 115 circuit just traced atthe same time closinga locking circuit from ground over contact of relay1, winding and front contact of relay 14, through the resistance 21 andwinding of relay 22 to battery. Relay 22 is energized andcloses acircuit through relay 15 individual to the four-wire circuit R andthrough the windings of similar relays not shown in parallel to therelay 15 and individual to other four-wire circuits; Relay 15 and thecorresponding relays of other fourwlre circuits are energized to openthe ini- I tial energizing circuit' of relay 14 which is individual tothe four-wire circuit R and similar relays individual to other four-wire13"0' circuits to revent the selection of the artilay120 to ground...Relay 17, upon being'en- .ergized, at its middle-contact closes'a ofi'cial'line 1 by, any other four-wire circuit. Belay; 20, upon being'energized, disconnects ltsown winding from the selectlng c1rcu1t abovedescribed and" closes a locking circuit 7 fmin-batteryover the contactof relay 3 and through the windingand'front contact of recking circuitfrom groundthrough the f winding'of relay 23, looking winding and frontmiddle contact of'relay 17' to point '12, and. thence' over the frontcontact of relay, 3 to battery: aRelays 1 7 an'd'j23 are nowenergizedqand at their vupper and lower contacts disconnect seriesnet-works WN, WN,.from the talking conductorsof line WRe1ay-17fatjtsupper and lower front contacts completes the talkingcircuit ofthe, line W oversaid contacts and the upper; and lower backcontactsof relays 24 and 25 y through thewinding of auto transformer 26to the midpoints of windings 27 and. 28 of a threc=winding induction.coil connected in circuit with the'two-wire line L an the artificiallineN [It will thus be seem that the line W is connectedto the two-wirline iL, without the interposition of any mission controlling net-work. Uponthe-energization of relay 18 a locking. circuit is also closed "by saidrelay fro ground '1 through the Winding of relay 29 and from the line Eover the upper and lower through the locking winding and middle I"front'contact of relay 18 to point .12., and

35 battery. Relays 18I'and 29 are now enerthence over the front contactof relay 3 to gized andv at their upper and lower contacts disconnectthe net-works EN BN and E151 from the line E The relay 18 at its outerfront contacts closes a direct connection back contacts ofrelays 30 and31 to the ter-. minals of the winding 32 of the three-windingtransformer, whereby the line E is inductively' connected to the line Lwithout 'the interposition of. any transmission concompleted.

trolling net-work s};

I The'talkin" connection at station A is now eturning to station D upontheinsertion'of the plug P in ack' J -of the four-wire system a circuitis closed from ground through the winding ofrelay 33, sleeve contacts ofjack J 8 and plug P and through both windings of relay 32 to battery.Relay 32 is energized butrelay 33 is marginal. and does not pull, up itsarmature. Upon inserting plug P in jack J 5 a circuitjs closed throughthe winding 34:, sleeve contacts of jack J and plug 'P' and through bothwindings of relay 35 to" battery. Relay 35 is energized over thiscircuit and at its lower contact closes a circuit through the winding ofrelay 36:

Relay36 upon being energized short cir-' and.

cuits the lower winding of relay 32 over a path from battery, frontcontact of relay I 36 and left-hand back contact of relay 37, wherebythe resistance in series wlth relay 33. is reduced so that said-relayreceives a suflicient amount of current to energize its winding.Similarly relay 32, upon being. energized short circuited. the lowerwinding of relay 35 over a path from battery,'fr0nt 1 contact ofrelay32"and back contact of relay,37. The relay 33, upon being energizedopens the shunt path through resistances 38 1 land 73, normally bridgedacross the termi-r nal conductors of the four-wire vcircuit at stationD, and short-circuits resistances 71' and 72, at the same timeconnecting artificial arrangements in circuit a balance is obtained suchthat; the transmlssion' over the fourvrire circuit is satisfactory forany condition in which the operators set is bridged across the two-wireterminals of the system, whether-a two-wire line be associatedtherewither-not. When said shunt and series re sistances are. removed,which occurs only whenboth plugs P and P are inserted inthe'corresponding jacks with the talking and 80,. 1 w line N in circuit.With these impedance ringing keys ofthe cord circuit normal, so

. that two-wireline is connected to the fourwirelcircuit,thevtransmission is increased to a value suitable for the throughconnection with 'a terminating. two-Wire line,

A talking connection .is now established.

betweenlines L and L over the four-wire circuit 'R. The incoming signalsfrom line L are'transmitted over the cord circuit C to the terminatingconductors of the four-wire circuit Rat station A, and thence throughthe windings 27 and 28 to the artificial line N The current flowvthrough windings 27 and 28 induces similar currents in Winding 32wherebythe' signals are transmitted over v the back contacts of relay 31and 30 and the front contacts-of relay 18 tothe line E and over saidline to the repeater The .repeater RE amplifies the signaling cur-,rents which are then transmitted over the line E and through windings ofan auto transformer 39 to the midpoints of windings a0 and 4:1 of athree-winding induction coil.'

balances the line L substantially no energy.

applied to the line W through the windmg 42 of -the three Windinginduction coil. Similarly'incomingsignals from line L are transmittedover the cord circuit C, to the terminating conductors of the can lay 1opens the locking circuit through relay 'RW now amplifies the signalswhich are then transmitted over the line W and over the front contactsof relay 17 and the back contacts of-relays 24 and25 through the autotransformer 26' and to t the midpoints of the windings 27 and28 wherethe energy di- Yides, one-half being transmitted to the artificial lineN the other half over the cord circuit C to the line L Ifthe line L is'tial 'pro ferly balanced by net-work N, substani;'- noenergyistransmitted through the winding 32'back tothe station If theoperator at station A should throw one of her controlling keys suchas-the listening ke 44 of the cord circuit C, a circuit will be c osedover the contact 45 of said key through the windingof relay. 10 whichupon being energized, at its upper and lower contacts 0 ens the circuitspreviously traced whereby. attery was applied directly to the sleevecontacts of plugs P. and P. The

potential over these contacts is 'now reduced sothat relays 1 and 3 arede'nergized. Re-

14 and relay 22 so-that these relays are deenergized, relay '14disconnecting the artifi- .cial line N from the repeater and relay'22opening the circuit of relay and similar relays of other -four-wirecircuits. Upon do energization of relay 3 the locking circuit previouslytraced. through relay is opened again bridges resistances 8 and 8' andconand said relay restored to 'normal. The de-. energi'zation'of relay 3also opens the circuit previously traced through relay 13' which nectsthe-series resistances 7. and 7' to the open the lockin terminatingconductors of the four-wire circuit to reduce the transmission to avalue suitable for terminal connections at station "A not involving twowire lines. The de enegization of the" relay 3 also operates to circuitspreviously traced through the win 'n 29 which are there y deefnergized,andthe connection of the transmission controlling net-works restored tonormal. Similarly if the operator at station D throws one of hercontrolling keys suchas the listening key .45? of cord circuit C, thecircuit is completed over' contact 46 of said key through the newreduced so that relay33 is deenergized, I

winding of relay 37 to'battery, whereby said relay is energized, and, atits right and lefthand contacts opens the short circuits previouslytraced for the ower windings of re- .lays 32' and '35. The tential overthe sleeve contacts of plugs. and jack J, is

'tact. Relay'50 also opens the momentary of'relays'17, 23,18 and cuit istoogreat, the operator may throw key K to the right instead of to theleft, thereby closing contacts 46 and 47. As "these con-' tacts-areconnected in parallel with contacts 9and 11 of keyK the circuits alreadydescribed are again closed whereby. the network N, is selected andconnected to the repeater and thetransmission controlling net-worksdisconnected from the four-wire line. When key K is thrown to the rightan additional contact 48 is closed whereby a circuit is completedthrough the winding and back contact of relay 49, back contact andwinding of relay 50, windings of relays 24and 30 to point 12 and thenceover the front contact of relay 3 to battery} Relaysv 49', 5Q, 24 and 30are thereby energized, relay 49 openin the momentary circuit just tracedand 100 g itselfi'over its front concircuit justclosed and at its frontcontact completes a. locking circuit from ground over the front contactand through the winding of relay. 50, through windings of relays 24 and30 to point'12', and thence over thefront contact of relay 3 to battery.Res lays 50,24 and 30 are maintained energized over this circuit. Relay24, at its middle contact closes a circuit from ground through thewinding of relay 25 over the front middle contact of relay 24 to point12 and thence over the contact of relay 3 to battery. Rejlays 24 and 25.at their upper" and lower front contacts introduce a net-work WN in. theconnection between the line W and the terminating-conductors of thefour-wire circuit. Similarly relay 30' closes a circuit work EN in theconnection between the line E, and the terminating conductors. of thefour-wire circuit. The inclusion 'of these two net-works in series withthe linesE and W reduces the transmission'over the fourwire circuit anarbitrary amount 'suflicient to prevent the undesirable result due totoo I great a transmission.

7 Upon taking down the connection the plugs P and P are withdrawn fromthe. correspon'dingjjacks, thereby deenergizing re--- ner alreadydescribed. Upon withdrawing plugs P and P from jacks J and J at station-D, relays 32, 33, 34, 35 and 36are. de-

energized and the apparatus controlled thereby restored to normal.

If the plug P-had been inserted in jack J of line L, instead of jack Jupon the operation of 'the'key K relay would havebeen energized therebycompleting the circuit from round overthe front contact of relay 50,winding and back contact of relay51,

back contact of relay 52 to point 5.3, and thence through the lowerwindings of relays '54 and- 5'5, through resistance 19, 'overthe Ibackcontac't-and through the winding of relay 20 and. over thefrontcontact of relay '3 to battery. .The energization of relay 51 "N,to the repeater. Relays 5. 1 and upon results the, connection ofartificial line being energized complete locking circuits through theirupper windings in series with relays 2'3 and 29 respectively. Relays 23and 29 operateas before to disconnect networks \VN and EN from the fourwire circuit, while relays 54 and 55 operate to interpolate the networksWN and EN, in the four-wire circuit. The connection of the net-workWN,extends from the line W overth'e'back contacts of relay 17 and the frontcontacts ofrelay 5 l'and thence over the circuit previously traced tothe terminating conductors of the four-wire circuit.

Similarly the connection of net-work- EN,

. extends from the line E, over the back conta'cts of relay 18 and thefront contacts of relay 55. The inclusion of these net works in thefour-wire system reduces the transmission to a value suitable for aconnection to the line L,. If the connection had been i to the line L,the relay 57 would have been energized. The energization of relay 57'closes a circuit from ground over the front contact of said relay,through the winding and back contactof'relay 58, back contact of relay59 to .point 60, and thence through the lower windings of relays 61 and62,

- through the resistance 19, back contact and winding of relay 20, andover the front contact of relay 3 to battery. Relay 58 operates I v toconnect network N, to the repeater while relays 61 and 62 close lockingcircuits --through windings of relays23 and 29 respectively andinterpolate. net-works W N and VVN, in the line W and net-works EN andEN, in the line E If the connection had been made to line 11,, relay 63'ould have been energized, closing a circuit l om ground over the frontcontact of relay 63, through the winding and back condelay 65 to point66 and thence through re tact of relay 64:, over the back contact of 3to battery. Relay'64 operates to connect artificial line RN tothe'repeater. It will be'notedthat the circuit just traced did not passthrough any of the controlling relays of the transmissioncontrolling'net-works, so'that net-works WN WN and WN, are all threeincluded in linev W while network s EN EN and EN 4 are included in lineE The circuit from line W extends over the back contacts of relay 17through net-work WN over-the back contacts' of relay 54 through net-WorkWN over the back contacts of relay 61 through net-work WN over backcontacts of relay 23, and thence over circuit previously tracedto theterminating conductors of the four-wire system. Similarly the connectionfrom line E -extends over the back contacts oi relays 135 5535621, 29,30 'and -31 tgiztheterminals of coil 32. "If-the connectionhad been madeto line L, rel. 67 would have been energized, thereby cl osing a circuitfrom ground over the front contact ofsaid relay, through the winding andback contact of relay 68, back contact of relay 69 to' point 66, andthence through resistance 19, back contact and winding of relay 2Q andover the front contact of relay 3 to battery. Relay 68 upon energizingalso connects the artificialline -RN tothe repeater. As no transmissioncontrolling relays are operated, the same networks are included inthe-four-wire circuit as described in connection with line L,.

, It will be noted that'a connection to eitherv line L, or line L,produces the same result as far as the selectionof an artificial line"and the adjustment of the transmission efliciency is concerned. It willbe under-. stood that these lines are illustrative of. a group havingsimilar characteristics, and while but two lines are shown, any desirednumber may be provided. It should also be noted that lines L L and L arepro-- vided with individual balancing lines N 4 N and N and that aconnection to each of these lines results in a 'dilferent adjustment ofthe transmission. As other lines having individual net works or othergroups of lines capable of being balanced by a common net work mightrequire the same transmission adjustment as one or more of the linesillustrated, the selecting circuitscontrol-led by said lines would beconnected to oneof the terminals 16, 53, '60 or .66, depending upon theadjustment desired.-

.It will be seen that by means of this invention, the transmission gaindue to the connection of two transmission circuits through a repeatermay be automatically determined in accordance with the articular 5circuits connected, thereby eliminating a consider. ble amount ofsupervision over connections. Whilethe invention has been disclosed asembodied in certain forms which are considered desirable, it will beunderthe Organization shown,

i said circuit; in accordance with .the require" ments of the line withwhich it is associated.- I

stood that various changes may be made" in J m. the spir t'of theinvention;

What is claimed is:

.1 A four-wire transmissioncircuit"ex? ichsaid circuit aplurality of;terminating lines with; which "said transmissioncircuit may (beassociated, .and means controlled by 'saidtenn-inating lines to "adjustthe transmission efiiciency-of 3.: A .f our wire repeater circuit"extending between widely separated stations, terminal apparatuswithwhich said repeater circuit cally' control I the transmissionefiiciency. of

said repeatercircuit in accordance .with the requirements of theterminal apparatus with which it-is associated. r

J 4. four-wire repeater'circuit-extending between widely separatedstations, .a olurality of transmission lines with which said re .peatercircuit. may be associated, and means.- controlled by said transmissionlines to ad: just the transmission efficiencyof said re- 1 peatercircuit in accordance with the require.

'ments of the line with which-it is associated,

53A 'repeat er circuit extending between widely separated .points andcomprising a .pair of separate transmission circuits one fortransmission in each direction and having one way'repeaters therein,terminal appara tus with-which said repeater circuit may he associated,and means-to automatically con'-- trol the transmission efiiciency ofsaid. re-. fipeater cirtnlit in-accordance with the ,re-

quirementsaof the terminal apparatus with which it is associated.

6. A, repeater. circuit extending 'between widely separated points andcomprising a,

pair of separate transmission circuitsone' fortransmlssion in eachdirection and hav ingone way repeaters therein, a plurahty of 1transmission lines with which said repeater circuit may be'associated,and means controlledby said transmissionlines to adjust,

the transmission efliciency -of v sai'd repeater circuit in accordancewith the requirements of the line with which-- it is associated.

'7. A repeater .c'lrcuit extending between .Widelyfseparated pointsandfcomprisingi a pair ofseparate transmiss on circuits one I- fortransmission. in "each direction and hav-v ing one way repeaterstherein, a, plurality of transmission'lines with which said repeatercircuit-maybe associated, a plurality of arti- 'ithou't departingcircuit ex 8; A repeater circuit extending between "Widely separatedpoints and comprising .a pair of separate transmission circuits one fortransmissionfin each directipn 'and having .one way; repeaters therein,"a pfurality of transmission lines with which said "repeater may. beassociated, a plur'ality of artificial lines to balance -saidtransmission lmes, and

means controlled by said lines for selecting I an artificial lineto'balance the transm1ss1on line with which the repeater'circuit'isassoeiated -and .;fo'r controllingthe transmission ance with theQrequirements of said -trans- I nissionlinesl. maybe-'assoc1ated,'and"mcans to automath' I 9. A repeater circuit"extendingbetween wldely separated po nts and comprising a pair of'separatetransmission circuits one for transmlsslon in each direct on and hav-.

ing one way repeaters therein, a plurality .of transmission lineswithwhich said re:v peater circuit may be associated, a plurality- .ofartificial ilines tobalance said transmissionilines; and arelay-selecting circuit for controlling theselection of an artificialline to balance the transmission line with which said repeater circuitmay be associated and for controlling the transmission efficiency ofsaid repeater circuit in accordance with the requirements, of thetransmission line i withwhichthe repeater circuit is associated.

I 10. A four wire transmission circuit. ex tending between widelyseparated stations,

a plurality oftenninating lines with which said transmission circuitmaybe associated, mea'ns controlled bysaid terminating lin'esj to adjustthe transmission efficiency of said circuit in accordance with therequirements of the line Withwhich-itis associated, and meanscontrollable" at will to vary" theadjustment thus obtained; I 11. Arepeater -circuit',-transmission lines transmission. efliciency of saidrepeater cir- I cuit in accordancewith whether it. is asso'ciated .witl1 a transmission line or with a terminal connection of anothercharacter.

'12 A four wire transmission circuit ex-. .--tend1ng between wldelyseparated stations,

a plurality of terminating lineswith which said c1rcu'1tmay 'beassociated, a plurality of. relays for variably controlling thetransbeingv selectively operated in accordance circuit is associated.

'efliciency of said .repeater circuit in accord-.

with' which said repeater circuit may be asmission efficienc'y of saidcircuit, said relays 13. A -fourwvire transmission circuit extendingbetween Widelyse arated stations,

iaplurality-df terminating ines with whichsaidcircuit-nmy be associated,certain of fsaid lines being grouped, arplurality'of re- "laysforvariably controlling .the transmission efficiency of said circuit,certain of said relaysbeing individual to groups of lines 145Atransmission circuit, terminating 'lines' with which said circuit may beas .}'sociated, a plurality of impedance elements,

a plurality of controlling relays selectively sociationj of said circuitwith a line to Varivresponsive to the association of said circuit- Witha line, and means controlled by said relays to variably interpolate'saidimpedance elements in the transmission circuit.

a plurality' of controlling relays selectively 1 5. .A- transmissioncircuit, terminating" 111185 wlth WlllCll SfiJd transmission circuit maybe, associated, a plurality of net-Works,

works in the, transmission circuit. j 16. A- transmiss onClIOllltflE-tefflglhfltlllg lines with i' which said transmissioncircuit may be associated, a plurality of impedance elements, and meansselectively controlled:

.by the association of said circuit with a line 'to" variably introducesaid impedanoerele men'ts'in said circuit'. v r

17. A transn issionclrcu t, terminating lines with which.said-ltra'nsmission 1 circuit may be associated, a jzliirality ofnet-works and-means selectively-J controlled by'the asably introducesaid netorks. in said circuit, In testimony-whereof, we have signedJournames to this's pecification this ninthday of October, 191?:

JOHN F. TOOMEY. CHARLES s. DEMARE'ST.

five cents each, by addressing the "Commissioner of IEatents-Washington, 2*). 0.

